Filter device for extruders and injection moulding machines

ABSTRACT

A filter device for extruders and injection moulding machines designed to process thermoplastics, comprising filter elements that are fitted in at least two separate ducts of a housing between at least one main admission duct and one main exit duct and are interchangeably mounted in sieve carrier bolts in sieve openings that can be moved inwards and outwards with said sieve carrier bolts in the respective bore hole of the housing. At least one locking mechanism is provided in the vicinity of the main admission duct upstream from the sieve carrier bolts. When in a flow position, the locking mechanism does not impede the flow of plastic from the main admission duct to the filter elements. However, when the locking mechanism is in a locking position, the flow of plastic in a partial admission duct is separated from the main admission duct, whereby a) the filter elements in the sieve carrier bolts are configured in an oval shape in a manner that is known per se, whereby the long axis of the oval extends in the direction of displacement of the sieve carrier bolts and the length of the oval axis of the filter elements in relation to the length of the housing bore hole is selected in such a way that only the length of the sieve carrier bolts required to seal the sieve carrier bolts in the housing bore hole is devoid of filter elements and b) the partial admission ducts for each sieve opening open out into at least two flow ducts.

CROSS-REFERENCE TO RELATED APPLICATIONS

Not Applicable

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH

Not Applicable

REFERENCE TO A “MICROFICHE APPENDIX”

Not Applicable

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention concerns a filter device for extruders and injectionmolding machines according to the precharacterizing clause of the mainclaim.

2. Description of the Related Art

A filter device representing this type is described in DE 42 18 756 C1.

From DE 295 17 140 U1 a filter device has become known in which an ovalsieve is inserted into the sieve bolt. With this previously known formof embodiment it is a matter of a sieve exchanger in which the extrudermust be turned off during the sieve exchange, so that the seal lengthbetween the material duct and the housing outer edge may be smaller thanin the case of a continuous sieve exchanger.

BRIEF SUMMARY OF THE INVENTION

The object on which the invention is based is to make available in afilter device of the generic type a large sieve surface that, however,is arranged in a relatively small housing, so that the entirearrangement is not built larger than the filter devices that are usualin the prior art. Achieved through the large sieve surface is a longservice life and, furthermore, good filtering results with normalthroughput, in comparison to the normal sieves that are usual in theprior art. Thus, an increase in throughput in comparison to normalsieves is aimed at.

This object forming the basis of the invention is accomplished through afilter device for extruders and injection molding machines forprocessing the plastics, with filter elements exchangeably arranged inat least two separate ducts of a housing between at least one mainadmission duct and at least one main outlet duct in sieve carrier boltsin sieve openings, which filter elements can be pushed in or pulled outwith the sieve carrier bolts arranged in the respective housing bores;in this, in the region of the main admission duct at least one blockingmeans is arranged in front of the sieve carrier bolts, which blockingmeans in the flow position does not hinder the stream of plastic movingfrom the main admission duct to the filter elements, but which in theblocking position separates the flow of the plastic in a partialadmission duct from the main admission duct, characterized by the factthat:

a) the filter elements in the sieve carrier bolts are formed as ovals ina manner known per se, the long axis of the oval extending in thedirection of the displacement of the sieve carrier bolts and the lengthof the oval axis of the filter elements with respect to the length ofthe housing bore in the housing being chosen in such a manner that onlythe length of the sieve carrier bolts necessary for the sealing of thesieve carrier bolts in the housing bore is free of the filter element,

b) and the partial admission ducts each open into a sieve opening in atleast two inflow ducts.

Advantageous developments of the invention include but are not limitedto the following.

The filter element may include ventilation grooves formed in the sievecarrier bolts and connected with the sieve openings that accommodate thefilter elements.

Provision may be made for at least one outflow duct for each sieveopening.

The blocking means may be formed by a bolt that traverses the mainadmission duct and is adjustable transversely to the flow direction ofthe plastic stream to be filtered, and the flow path from the mainadmission duct to the admission ducts may be formed by a narrow sectionin the outer periphery of the bolt.

A main discharge duct may be present in the bolt, which duct opens atone end into the atmosphere and to which are connected two partialdischarge ducts, which upon displacement of the bolt can be brought intoa fluid connection with one or the other partial admission duct In thefluid connection of the partial discharge ducts with the associatedpartial admission ducts, the flow cross-section in the transition regionbetween the partial admission ducts and the partial discharge ducts maybe smaller than the flow cross-section of the partial admission ducts.

The blocking means may be arranged in the housing of the sieveexchanger.

The blocking means may be arranged in its own housing, which isattachable to the housing of tee filter device.

The bolt may be round in shape and the narrow section is designed overthe entire circumference of the bolt.

The bolt, on its side facing the main admission duct, may displays abypass duct that, depending on the position of the bolt, is able toproduce a connection between the main admission duct and the outsideatmosphere.

The opening of the bypass duct into the main admission duct may bearranged so that the main admission duct can be brought into fluidconnection with both the narrow section and the bypass, but that throughadjustment of the bolt the connection between the main admission ductand the narrow section is closable while the connection between the mainadmission duct and the bypass duct is open.

The bolt of the blocking means, in addition to its movement in thelongitudinal axis, also may be rotatable around the longitudinal axis.

This object forming the basis of the invention is also accomplishedthrough blocking means for controlling the throughput of a flowablemedium, with filter elements arranged in at least two separate ducts ofa housing between at least one main admission duct and at least one mainoutlet duct, the blocking means being arranged in the region of the mainadmission duct in front of the filter elements;

and in the flow-through position not hindering the flow of the flowablemedium from the main admission duct to the filter elements, but in ablocking position separating the flow-through of the medium in anadmission duct from the main admission duct, characterized by the factthat the blocking means is formed by a bolt, arranged in a housing,which bolt traverses the main admission duct and is adjustable adverselyto the flow direction of the flowable medium, and tat the flow path fromthe main admission duct to an outlet duct is formed by a narrow sectionin the outer periphery of the bolt.

Advantageous developments of the invention may also include but are notlimited to the following.

The narrow section may be designed so as to allow an efficient flow.

The blocking means may include a main discharge duct in the bolt, whichduct on one end opens into the atmosphere and connects to two partialdischarge ducts, which upon a displacement of the bolt can be broughtinto fluid connection with one of the partial admission ducts.

During the fluid connection of the partial discharge ducts with theassociated partial admission ducts the flow cross-section in thetransition region between the partial admission ducts and the partialdischarge ducts may be smaller tan the flow cross-section of the partialadmission ducts.

The blocking means may be arranged in its own housing, which isattachable to the housing of the filter device.

The blocking means may be arranged in the housing of the sieveexchanger.

The bolt may be round in shape and the narrow section is designed overthe entire circumference of the bolt.

The bolt, on its side facing the main admission duct, may display abypass duct that, depending on the position of the bolt, is able toproduce a connection between the main admission duct and the outsideatmosphere.

The opening of the bypass duct into the main admission duct may bearranged so that the main admission duct can be brought into fluidconnection with both the narrow section and the bypass, but that throughadjustment of the bolt the connection between the main admission ductand the narrow section is closable while the connection between the maadmission duct and the bypass duct is open.

The bolt of the blocking means, in addition to its movement in thelongitudinal axis, also may be rotatable around the longitudinal axis.

Expressed in different words, it is proposed that the sieve in eachsieve carrier bolt is designed so as to be virtually the size, i.e. thelength considered in the displacement direction of the sieve carrierbolt, of the actual housing that accommodates the sieve carrier bolts.In this, there arises the difficulty that during the extracting of thesieve, i.e. of the filter element, the latter already comes into contactwith the atmosphere in a peripheral region of the filter element, sothat a flowing out of the filtered and to-be-filtered plastic occurs.Thus, it must be ensured that, at the moment when the sieve carrier boltbegins its pulling-out movement, the partial admission duct, assigned tothis sieve opening, of the main admission duct is closed off. On theother hand, it must be ensured that during the driving in of the sievecarrier bolt to its filtering position a pre-ventilation of the sieveopening can take place, during which the partial admission duct assignedto the other sieve carrier bolt is still loaded with the plasticmaterial to be filtered. By virtue of this blocking position achievablethrough the blocking means, the possibility of a large, oval sievedesign comes about.

With the use of a large, oval sieve, according to the invention it isproposed that the admission ducts in each case open into two inflowducts, whereas, however, only one outflow duct can be planned for eachsieve opening. In this way, favorable inflow and outflow conditions areproduced.

The blocking means is preferable designed as a bolt, and this bolt,preferable arranged in an attachment housing, displays a flow openingfor the plasticized plastic material, the flow opening being formed bythe bolt's having a preferably circumferential narrow section, throughwhich can flow the stream of plastic. This narrow section leads into themouth of the two partial admission ducts. The bolt is displaceable in adirection transverse to the stream of plastic and displays in addition amain discharge duct and partial discharge ducts, which connect to themain discharge duct. Through a displacement of the bolt, a position cannow be attained in which the admission duct is connected to the partialadmission duct via the narrow section designed in the bolt. By means ofthe controls standard today, this bolt that forms the locking means canbe positioned such that, on the one hand, the partial admission ductleading to the sieve opening is completely closed off, and on the otherhand the possibility exists, despite the loading of the other partialadmission duct, of creating a connection to the other partial admissionduct, so that here a pre-flooding of the sieve opening is made possible.

In addition, the bolt designed according to the dependent claims makesit possible that when the bolt assumes a position in which the mainadmission duct is connected to the partial admission duct via the narrowsection designed in the bolt, the other partial admission duct isconnected via a partial discharge duct to the main discharge duct, sothat the loading of the mold connected to the filter device still takesplace, but at the same time the idle sieve can be run through from theclean side of the sieve towards the dirty side of the sieve and the dirtparticles removed here flushed back through the partial admission ductassigned to this sieve and then conducted via a partial discharge ductinto the main discharge duct. The main discharge duct here leads to theatmosphere.

The bolt designed as a blocking means displays, on its side facing themain admission duct, a bypass duct, which in dependence on the positionof the bolt is capable of producing a connection between the mainadmission duct and the outside atmosphere.

In addition, the invention relates to a blocking means for controllingthe throughput of a flowable medium independently of the subsequentlyconnected unit, for example the above described filter device. Theblocking means can also be used in conjunction with other flowable mediathat are to be controlled.

BRIEF DESCRIPTION OF THE DRAWINGS

An example of embodiment of the invention will be explained in thefollowing with the aid of the drawings. The drawings show:

FIG. 1: a filter device with two sieve carrier bolts and, in each case,a large, oval sieve arranged in each sieve carrier bolt

FIG. 2: the blocking position of the above sieve carrier bolt

FIG. 3: the pre-flooding position for the sieve opening in the abovesieve carrier bolt

DETAILED DESCRIPTION OF THE INVENTION

According to FIG. 1, arranged in a housing 1 are two sieve carrier bolts2 and 3, which in the represented example of embodiment are arranged oneabove the other. Designed in the sieve carrier bolts 2 and 3 are filterelements 4 and 5, which—as can be clearly seen in the drawing are formedas ovals, the long axis of the oval extending in the direction of thedisplacement direction of the sieve carrier bolts 2 and 3 and the lengthof the oval axis of the filter elements 4, 5 relative to the length ofthe housing bore in the housing 1 is selected in such a manner that onlythe length of the sieve carrier bolts 2, 3 required for the sealing ofthe sieve carrier bolts 2, 3 in the housing bore is free of the filterelement.

As can be seen from the representation according to FIG. 1, shortlyafter the beginning of the pushing-out movement of one or the othersieve carrier bolt 2 or 3, the peripheral edge face of the filterelement 4 or 5 in question already comes into contact with the outsideatmosphere, while the remaining portion of the filter element 4 or 5 isstill connected with the conveying of the filtered or to-be-filteredplastic material, so that here a direct connection between the feedstream of the plastic material or the outflowing stream of the plasticmaterial and the outside atmosphere would take place.

The displacement of the sieve carrier bolts 2, 3 takes place in a mannerknown per se, via hydraulic or electric devices, and is controlled bymeans of suitable controls, such as are generally customary in the priorart.

In order to prevent this harmful contact between the sieve opening andthe outside atmosphere, according to the invention provision is made fora blocking means 10, which in the represented example of embodiment isformed in conjunction with the housing 1 as follows:

The housing 1 displays a main admission duct 6 and a main outlet duct 7;provision can be made in front of the main admission duct 6 for a worm(not represented) by means of which the plasticized plastic material isfed to the main admission duct 6 under appropriately high pressure.Inside the housing 6 the main admission duct 6 divides into two partialadmission ducts 8 a and 8 b, which are connected with sieve openings 28and 29, respectively, in which are arranged the filter elements 4, 5.Connected to the clean sieve side of the sieve openings 28, 29 arepartial outlet ducts 9 a and 9 b, which lead to a main outlet duct 7.

Designed in front of the actual housing 1 of the filter device is anadditional housing, which accommodates the bolt 11 that is formed as ablocking means and displaceable transversely to the current direction ofthe stream of plastic by hydraulic, pneumatic, or other means. Leadinginto this housing 24 are, on the one side, extensions of the partialadmission ducts 8 a and 8 b and, on the other, opposite side, the mainadmission duct 6. Instead of an additional housing, the blocking meanscan also be arranged inside the housing 1.

The flow connection between the main admission duct 6 and the partialadmission ducts 8 a and 8 b is achieved through a narrow section in thebolt 11, whereby in the represented example of embodiment the bolt 11 isformed as a cylinder, i.e. round in cross-section, and the narrowsection 11 is formed on the entire outer circumference of the bolt 11.The apparatus formed by the housing 24 and the bolt 11 as well as themain admission duct 6 will be called the blocking means 10 in thefollowing; the bolt 11 can also be formed as a polygon. The bolt 11displays further a main discharge duct 16, which in the representedexample of embodiment extends centrally when viewed in the longitudinalaxis of the bolt 11 and which on one end opens into the atmosphere. Twopartial discharge ducts 14 and 15 extend transversely to thelongitudinal axis of the main discharge duct 16 and lead on one end intothe main discharge duct 16 and on the other end to the outer side of thebolt 11. Of course, other configurations of the main discharge duct orducts can also be designed.

In addition, the bolt 11 is equipped with a bypass duct 27, which isarranged in such a manner that it can be brought into a flow connectionwith the main admission duct 6, so that the material coming from themain admission duct 6 is not led to the partial admission ducts 8 a or 8b, but rather can be led out into the atmosphere. When the extruder isstarted, contaminated and chemically cracked molten material isdischarged via the bypass duct 27 to the outside and only after thisprocess is the production started.

In the representation according to FIG. 2, the bolt is situated in sucha position that the narrow section 12 conducts the stream of plasticmaterial fed through the main admission duct 6 towards the partialadmission duct 8 b. From here the material reaches the filter element 5.

FIG. 3 shows that through a slight displacement of the bolt 11 thenarrow section 12 can come into contact also with the partial admissionduct 8 a, so that a pre-flooding of the sieve opening 28 can be carriedout.

FIG. 1 further shows that each partial admission duct opens into itsassociated sieve opening in two inflow ducts 22 a, 23 a or 22 b, 23 b,respectively, so that very favorable inflow conditions are attained forthe large, oval filter elements 4 and 5. FIG. 1 should also make clearthat for each sieve opening 28, 29 only one outflow duct, 21 a or 21 b,respectively, is provided.

With the filter element 4 or 5 formed according to the invention, a longservice life for large sieve surfaces is achieved, as well as goodfiltering results with normal throughput compared to a normal sieve. Anincrease in throughput compared to normal sieves is also possible. Alsoachieved through the use of the above described blocking means 10 is thefact that this blocking means can be used with differently designedextruder arrangements in the simplest manner as a startup valve and forreverse rinsing, so that with such a blocking means the most varioustasks can be accomplished in filter devices for extruders and injectionmolding machines.

The blocking means 10 described above, i.e. the bolt 16 arranged in ahousing 17, can also be used to control other flowable media, i.e. itneed not strictly be a matter of a stream of plastic that is controlledby it, but rather the advantages of the blocking means 10 describedabove and placed under protection in the dependent claims can be madeuse of independently of the medium to be controlled.

What is claimed is:
 1. Filter device for extruders and injection moldingmachines for processing thermoplastics, comprising: a housing definingtherein at least one main admission duct and at least one main outletduct connected thereto, said housing also defining at least two sieveopenings therein between said at least one main admission duct and saidat least one main outlet duct; sieve carrier bolts disposed within saidsieve openings, said carrier bolts defining ducts therein, said carrierbolts being displaceable within said sieve openings; filter elementsexchangeably arranged in said ducts in said sieve carrier bolts; atleast one partial admission duct connecting said main admission ductwith said filter elements at least one blocking means moveable between aflow position wherein said blocking means does not hinder a flow ofplastic moving from said main admission duct to said filter elements anda blocking position wherein said blocking means prevents the flow ofplastic from the main admission duct to the at least one partialadmission duct, wherein a) said filter elements in said sieve carrierbolts are formed in a shape of an oval, a long axis of the ovalextending in a direction of a displacement of said sieve carrier bolts,a length of the long axis of the oval being such that only a length ofsaid sieve carrier bolts necessary for sealing said sieve carrier boltsin said sieve openings is free of said filter elements; and b) each ofsaid at least one partial admission is connected to at least one of saidsieve openings with at least two inflow ducts.
 2. Filter deviceaccording to claim 1, filer comprising ventilation grooves defined insaid sieve carrier bolts, said ventilation grooves being connected withsaid sieve openings.
 3. Filter device according to claim 1, furthercomprising at least one outflow duct for each of said sieve openings. 4.Filter device according to claim 1, wherein said blocking meanscomprises a bolt that traverses said main admission duct, said boltbeing adjustable transversely to a flow direction of the flow ofplastic, said bolt comprising a narrow section in an outer periphery ofsaid bolt such that plastic may flow past said bolt at said narrowsection.
 5. Filter device according to claim 4, further comprising amain discharge duct defined in said bolt, said main discharge duct beingopen at a first end to atmosphere, said bolt further defining twopartial discharge ducts connected with said main discharge duct, whereinsaid bolt is displaceable such that at least one of said partialdischarge ducts can be brought into fluid connection with each of saidpartial admission ducts.
 6. Filter device according to claim 5, whereina flow cross-section in a transition region between said partialadmission ducts and said partial discharge ducts is smaller than a flowcross-section of said partial admission ducts.
 7. Filter deviceaccording to claim 1, wherein said blocking means is arranged in saidhousing.
 8. Filter device according to claim 1, wherein said blockingmeans is arranged in a further housing, said further housing beingattachable to said housing.
 9. Filter device according to claim 4,wherein said bolt is round in shape, and wherein said narrow sectionextends around an entire circumference of said bolt.
 10. Filter deviceaccording to claim 4, wherein said bolt defines a bypass duct on a sideof said bolt facing said main admission duct, said bolt being moveableto produce a connection between said main admission duct and atmosphere.11. Filter device according to claim 10, wherein said bypass duct isarranged such that motion of said bolt can bring said main admissionduct into fluid connection with both said narrow section and saidbypass, and such that motion of said bolt can bring said main admissionduct and said bypass duct into fluid connection without bringing saidmain admission duct and said narrow section into fluid connection. 12.Filter device according to claim 4, wherein said bolt is rotatablearound a longitudinal axis thereof.
 13. Blocking means for controllingthroughput of a flowable medium within a housing, said housingcomprising at least one main admission duct and at least one main outletduct connected thereto, and at least two filter elements in separateducts therein, said housing further comprising at least one admissionduct connecting said filter elements to said main admission duct, saidblocking means comprising: a bolt disposed between said main admissionduct and said filter elements, said bolt being movable between a flowposition wherein said bolt does not hinder a flow of the flowable mediumfrom said main admission duct to said filter elements and a blockingposition wherein said bolt prevents the flow of the flowable medium fromthe main admission duct to said at least one admission duct, whereinsaid bolt traverses said main admission duct and is adjustabletransversely to a flow direction of the flowable medium, and said boltcomprises a narrow section in an outer periphery of said bolt such thatthe flowable medium may flow past said bolt at said narrow section. 14.Blocking means according to claim 13, wherein said narrow section isdesigned so as to allow an efficient flow.
 15. Blocking means accordingto claim 13, wherein said bolt defines a main discharge duct therein,said main discharge duct being open at a first end to atmosphere, saidbolt further defining two partial discharge ducts connected with saidmain discharge duct, wherein said bolt is displaceable such tat at leastone of said partial discharge ducts can be brought into fluid connectionwith each of said partial admission ducts.
 16. Blocking means accordingto claim 13, wherein a flow cross-section in a transition region betweensaid partial admission ducts and said partial discharge ducts is smallerthan a flow cross-section of said partial admission ducts.
 17. Blockingmeans according to claim 13, wherein said block means is arranged in afurther housing, said her housing being attachable to said housing. 18.Blocking means according to claim 13, wherein said blocking means is aarranged in housing.
 19. Blocking means according to claim 13, whereinsaid bolt is round in shape, and wherein said narrow section extendsaround an entire circumference of said bolt.
 20. Blocking meansaccording to claim 13, wherein said bolt defines a bypass duct on a sideof said bolt facing said main admission duct, said bolt being moveableto produce a connection between said main admission duct and atmosphere.21. Blocking means according to claim 20, wherein said bypass duct isarranged such that motion of said bolt can bring said main admissionduct into fluid connection with both said narrow section and saidbypass, and such that motion of said bolt can bring said main admissionduct and said bypass duct into fluid connection without bringing saidmain admission duct and said narrow section into fluid connection. 22.Blocking means according to claim 13, wherein said bolt is rotatablearound a longitudinal axis thereof.